Pyridine-3,4-dinitriles



Patented Mar. 20,

t H PYRlDINE-3,4-DINITBJLES Richard Kuhn and Otto Westphal, Heidelberg, Germany, assignors to Winthrop Chemical Company, Inc., New York, N. Y., a corporation of New York No Drawing. Application January '26, 1940, Serial No. 315,746. In Germany January 27, 1939 This invention relates to pyridine 3.4-dinitriles or' -4.5-dinitriles, and to a process of pre-.

paring the same.

In accordance with the present invention pyridine-3.4-dinitrileswhich are identical with pyridine-4.5-dinitriles can be obtained by reacting upon pyridine-3.4-dicarboxylic acid diamides or -4.5-dicarboxylic acid diamides respectively, with an agent; capable of splitting ofi water from the carboxylic acid amide groups, such as acid anhydrides of the type of acetic anhydride and phosphorus pentoxide, furthermore acid halides of the type of phosphorus oxychloride and thionylchloride. The said pyridine- 3.4-dinitri1es are formed as the main products together with other reaction products upon heating of the pyridine-3.4-dicarboxylic acid diamides with the agent capable of splitting off water if the time of heating is properly adjusted to the quantity and the particular type of the initial material. Larger quantities of the initial material require a prolonged reaction time.

It is most surprizing that by such chemical dehydration the pyridine-3.4-dicarboxylic acid diamides can be transformed relatively easily into the corresponding pyridine-3.4-dinitriles in view of the fact'that pyridine-2.3-dicarboxylic 2 grams 5-bromo-pyridine 3.4-di-carboxylic acid diamide (well dried by means of phosphorus pentoxide at 70 C.) are boiled under reflux with 30 cos. of acetic anhydride for 4% to 5 hours. 7

After the first hour all matter has dissolved. After 4-5 hours the yellow solution'be'comes noticeably brown. It is cooled and treated with excess, absolute methanol. The mixture is stored for some time and then freed under reduced pressure from ethyl acetate and acetic acid, the oily residue is once more treated with methanol and the solution again evaporated under reduced pressure. The brown oil residue is sublimed at 0.03 mm. pressure. The fi-bromo pyridine-3.4-di-carboxylic acid dinitrile sublimes at -80 C. in shining solid rosettes (with a yield of about 50%). Above 0. other products are obtained. When again sublimed or recrystallized from chloroform-petroleumether snow white crystals are obtained melting at C. with an extremely bitter taste.

The residue of the sublimation can be boiled again for 3 hours with acetic anhydride (25 ccs.). There are obtained still about 10% of the dinitrile.

If the mixture is boiled for a too short time, the yield of dinitrile is by far worse, if it is boiled for a too long time, apart, from the dinitrile a mononitrile is obtained, which already sublimes I at 40 C. under 0.03 mm. pressure (shining, starshaped needles melting t 69 C.). When starting with the twofold quantity of the startingmaterial, it is preferably heated for 6 /2 hours.

Example 2 2.6 grams of 2-methyl-3-methoxy-pyridine-4.5-

dicarboxylic acid diamide are boiled for 4 hours.

4.5-dicarboxylic acid are dissolved in methanol and treated with excess ethereal diazomethane solution. After 12 hours the solvent. is distilled oii and the residue is distilled under 1 mm. pressure at 126 C. The dimethylester thus obtained is shaken with 200 cos. of aqueous ammonia solutionuntil it has dissolved and then cooled. After some time white crystals of the 2-methyl-3- methoxy-pyridine-4.5-dicarboxylic diamide have separated. They melt at 245 C. (not sharply) while decomposing.

We claim:

1. A pyridine-3.4-dinitrile.

2. 2-Methyl-3-methoxy-pyrldine-4.5-dinitrile.

3. 5-Bromo-pyridine-3.4.-dinitri1e. -4. The process for preparing a pyridine-3.4-

dinitriie which comprises reacting upon a pyridine-3.4-dicarboxy1ic acid diamide with an agent capable of splitting ofl water selected from the group consisting of acetic anhydride, phosphorus, pentoxide, phosphorus oxychloride and thionyl chloride.

reacting upon 2-methyl-3-methoxypyridine-4.5- dicarboxylic acid diamide with acetic anhydride while boiling.

5. The process for preparing 2-methy1-3- methoxy-pyridine-4.5 dinitrile which comprises reacting upon 2-methy1-3-methoxypyridine-4.5-

dicarboxylic acid diamide with an agent selected from the group consisting of acetic anhydride,

phosphorus pentoxide, phosphorus oxychioride and thionyl chloride.

6. The process for preparing 2-methy1-3- tmethoxy-pyr1dine-4.5-dinitrile which comprises '7. The process. for preparing a pyridine-3.4- dinitrile, which comprises reacting upon a pyridine-3.4-dicarb0xy1ic acid diamide with thionyl chloride.

8'. The process for preparing 2-methy1-3- methoxy-pyridine 4.5-dinitrile, which comprises reacting upon 2-methy1-3-methoXy-pyridinedicarboxylic acid diamine with thionyl chloride.

9. A 2-methy1-3-1ower a1koxy-pyridine- ,5-dinitrile.

RICHARD KUHN. O'ITO WES'I'PHAL. 

